The present invention relates to a magnetic disk apparatus and is especially adapted for a magnetic disk apparatus that records information on a magnetic disk by a vertical magnetic recording method.
In a magnetic disk apparatus adopting a vertical magnetic recording method, in a case where a magnetic field is applied from the outside, there is the possibility that the following problem takes place. An external magnetic field is concentrated in the main magnetic pole by the magnetic head and data recorded on the disk is destroyed because of the structure of the magnetic head. Since it is impossible to weaken the strength itself of the external stray magnetic field applied to the magnetic disk apparatus, it is necessary to impart a function of producing a shielding effect (weakening the strength of the external magnetic field) against the external magnetic field to the magnetic disk apparatus.
Accordingly, one shown in JP-A-2003-77266 (Patent Reference 1) has been devised as a conventional magnetic disk apparatus. The magnetic disk apparatus of this Patent Reference 1 is constructed to consist of a magnetic disk of a rotary disk type for recording information by a vertical magnetic recording method, a magnetic head for recording information on the magnetic disk or playing back information from the magnetic disk, a disk drive mechanism that supports movably the magnetic head in a radial direction of the magnetic disk, an enclosure, and a shield member made of a magnetic material for magnetically shielding the magnetic head, the enclosure being made up of a base and a cover.
In an embodiment associated with FIGS. 1-16 of Patent Reference 1, the magnetic disk, magnetic head, and disk drive mechanism are accommodated within the enclosure. The shield member is mounted over the top, lower, and side surfaces of the outside of the enclosure including spaces located above and under the range of movement of the magnetic head (Prior Art 1).
In an embodiment associated with FIG. 17 of Patent Reference 1, magnetic disk, magnetic head, disk drive mechanism, and shield member are accommodated within an enclosure. A shield member is mounted only on the base portion and cover portion which are opposite to the magnetic head (Prior Art 2).
Furthermore, in an embodiment associated with FIG. 18 of Patent Reference 1, magnetic disk, magnetic head, and disk drive mechanism are accommodated within an enclosure. A cutout portion is formed in a part of the enclosure. A shield member is installed in the portion. The front-end side of the shield member extends to both sides of the magnetic disk. Its end surface is positioned oppositely to an end surface of the magnetic head (Prior Art 3).
In addition, in an embodiment associated with FIG. 19 of Patent Reference 1, magnetic disk, magnetic head, and disk drive mechanism are accommodated within an enclosure. A recessed portion is formed in the outer surface of the enclosure. A shield member is installed in the recessed portion. The front-end side of the shield member extends to both sides of the magnetic disk. Its end portion is located oppositely to an end portion of the magnetic head (Prior Art 4).